The present invention relates to a power reception control device, a power reception device, a non-contact power transmission system, a charge control device, a battery device, and an electronic instrument.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charging a household appliance (e.g., cordless telephone handset or watch), and the like have been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device using a primary coil and a secondary coil, for example. JP-A-2006-166619 discloses the circuit configuration of a charging device for a secondary battery (e.g., lithium-ion battery), for example.
Since a related-art non-contact power transmission device is configured so that a power-reception-side control circuit merely has a power reception function and a function of controlling power supplied to a battery (e.g., battery pack), a dedicated charge control circuit controls a charging current (and a charging voltage) supplied to the battery.
According to this configuration, the non-contact power transmission system cannot positively control the charging current (charging voltage) supplied to the battery. Therefore, the functions that can be implemented are limited.
It is important to take measures against a foreign object in order to improve the safety and the reliability of the non-contact power transmission system. Specifically, when power is transmitted in a state in which a metal foreign object is present, abnormal heat generation may occur. In this case, power transmission must be stopped. A metal foreign object may be small or medium-sized, or may be large (e.g., a thin sheet which is present over the entire area between a primary-side instrument and a secondary-side instrument). Therefore, it is desirable to take appropriate safety measures irrespective of the size or type of foreign object.
For example, when a thin sheet-shaped metal foreign object is inserted to completely block a primary-side instrument and a secondary-side instrument during power transmission, the primary-side instrument device may erroneously regard the metal foreign object as the secondary-side instrument and continue power transmission. Such an erroneous power transmission state is hereinafter referred to as “takeover state”. It is difficult to detect the takeover state using related-art technology.